Polyarylene sulfide (hereinafter, sometimes abbreviated as PAS) represented by polyphenylene sulfide (hereinafter, sometimes abbreviated as PPS) has suitable characteristics as an engineering plastic such as excellent heat resistance, barrier property, chemical resistance, electrical insulation property and moist heat resistance, and is used mainly in injection forming and extrusion forming of various electrical and electronic component parts, machine component parts and motor vehicle component parts, films, fibers and the like.
The use and deployment of powder/grain materials of such excellent PAS resin for various forming processes and as a coating agent and a heat resistant additive is highly demanded. As for the method of producing a PAS resin powder/grain material, various methods as indicated below have been proposed.
In Japanese Unexamined Patent Publication (Kokai) No. HEI 10-273594, PPS as islands and another thermoplastic polymer as sea are melted and kneaded to form a resin composition having a sea-island structure, and then the sea phase is subjected to dissolution and washing to obtain a PPS resin powder/grain material. Furthermore, in Japanese Unexamined Patent Publication (Kokai) No. 2007-154166, PPS is dissolved in a solvent at high temperature and then cooled for precipitation, whereby a PPS resin powder/grain material is obtained.
Furthermore, as a method of improving the fluidity of a resin powder/grain material, there is a method as described in Japanese Unexamined Patent Publication (Kokai) No. 2013-166667 in which an inorganic fine particle is added to increase the interparticle distance and therefore reduce the interaction between particles.
However, in the method described in Japanese Unexamined Patent Publication (Kokai) No. 2013-166667, it is difficult to resolve the deterioration in fluidity caused by compression in a lower portion of a silo or a hopper.
The PAS resin powder/grain material, because of its high electrical insulation property, is apt to undergo aggregation due to static electricity and is therefore not excellent in fluidity, and therefore gives rise to a problem that during a production process, trouble at the time of supply or discharge to or from the silo or the like may often occur. Furthermore, the PAS resin powder/grain material is high in compression degree so that in a lower portion of the silo or the hopper, the PAS resin powder/grain material is compressed because of the powder pressure and increases in bulk density, causing a further decrease in fluidity.
In particular, the PPS resin powder/grain materials obtained by the methods of Japanese Unexamined Patent Publication (Kokai) No. HEI 10-273594 and Japanese Unexamined Patent Publication (Kokai) No. 2007-154166 are small in particle diameter and, therefore, the area of contact with neighboring particles becomes large so that electrostatic aggregation of particles is likely to occur and therefore fluidity is poor.
It could therefore be helpful to efficiently obtain a polyarylene sulfide resin powder/grain material small in average particle diameter, excellent in powder fluidity and low in compression degree.